Question

A ferryboat traveling at a speed of 30 km/h attempts to cross a river with a current of 5 km/h. What is the boat's speed relative to the shore?

Answer 1

Answer on Question #45466 – Physics – Mechanics | Kinematics | Dynamics

Question:

A ferryboat travelling at a speed of $30\mathrm{km/h}$ attempts to cross a river with a current of $5\mathrm{km/h}$ . What is the boat's speed relative to the shore?

Answer:

We assume that ferryboat is travelling downstream.

The boat's motor is what carries the boat across the river the Distance A; and so any calculation involving the Distance A must involve the speed value labeled as Speed A (the boat speed relative to the water). Similarly, it is the current of the river that carries the boat downstream for the Distance B; and so any calculation involving the Distance B must involve the speed value labeled as Speed B (the river speed). Together, these two parts (or components) add up to give the resulting motion of the boat. That is, the across-the-river component of displacement adds to the downstream displacement to equal the resulting displacement.

Speed C = √Speed A² + Speed B²

Speed C = $\sqrt{30^2 + 5^2} \approx 30.4 \, \text{km/h}$

Answer: The boat speed relative to the shore is $30.4 \, \text{km/h}$

http://www.AssignmentExpert.com/